Drilling fluid containing explosive composition



DRILLING FLUID CONTAINING EXPLOSIVE COMPOSITION Original Filed May 26.1960 FIG.

SWIVEL I9 ENCAPSULATED EXPLOSIVE ROTARY I7 KELLY E T D .n V N E Mw ,R .dE T E N J O G A V O A L A LS T MN 1 P U D0 S X G so ESD N P L V l N R El. P T A X N R l A D A C F B E .l W v w. N O D A N "E HR E L U A m H H NC EN K A BOC R OEA G 2 R L J v.. u B 4 G 4 H 4 P4 D2 U M s n 2 B c a m I3 J v. ....V /l/ mm 1.7.1. f M G 2 m 3 w R T. S 3 L I R D lead picnateand gnhr dynamite.

United States Patent On ice il Patented Nov. 26, 1963 'Ilhe presentinvention is directed to the drilling of wells, More particularly, theinvention is concerned with a method for increasing the drilling rate inthe drilling of oil and gas wells land the like. In its more specificaspects, the invention is concerned with an improved drilling method inwhich drilling rates are increased by generation of gas adjacent thedrill bit.

This application is a tdivision of Serial No. 31,865, tiled May 26,1960, for Robert H. Friedman, Leon H. Robinson, Jr., and Jack H.Edwards, entitled Rotary Drilling of Wells Using Explosives.

The present invention may be briey described as a method for drilling awell with a drill bit in which a hollow drill string, having a drill bitattached to its lower end, is rotated and in which an aqueous drillinguid is circulated through a path of iiow detined by the hollow drillstring and the annulus between the drill string and the |wall of therwell. The specific feature of the present invention involvesintroducing into the circulating drilling iiuid a sufiicient amount ofwater soluble capsules containing an explosive which is renderedharmless by extended contact with water. The capsules have a size withinthe range from about 0.01 Ito about 0.25 inch and the explosive has asensitivity as measured by the dropsensitiv-ity test within the rangefrom about 2 to about l0 cm. The capsules are exploded by weight imposedon the capsules by the drill bit such that increased drilling rates areobtained.

The explosive employed in the practice of the present invention shouldbe an explosive which is moderately sensitive in the range from about 2to about 10' cm. as measured by the standard drop-sensitivity test. Thistest measures the height in centimeters; a 2 kilogram weight must bedropped to cause explosion. A description or" this test will be found inMeyer, Martin, Explosives, Thomas Y. Crowell, Co., New York, 1943, p.28, The preferred range of sensitivity is in the range from about `2 toabout 5 centimeters.

While the exact composition of the explosive is not critical, theexplosive must have the sensitivity set out hereinbefore. As examples ofthe explosives which are useful in fthe present invention, there may bementioned These explosives are within the preferred range ofsensitivity. Explosives that are in themselevs yabove the range ofsensitivity may be brought to the desired sensitivity by admixture withmore sensitive materials which function as igniters. Afdmixture servesto decrease the sensitivity of the more sensitive material and increasethat of the less sensitive material. Thus, by admixing such explosiveslas mencury fulminate, for example 80 percent mercury fulminate with 20percent potassium perchlorate; or antimony trisulfide, lead triazide, ornitrogen triiodide with standard explosives like dynamite,trinitrotoluene, and PETN (pentaerythritol tetranitrate), thesensitivity may be adjusted to a sensitivity within the desired range. Adesirable characteristic of the explosive -is that it is renderedharmless by contact with water. `Contact with water prevents dangerousaccumulation of the explosives in the drilling fluid.

The encapsulating agent for the explosive may be any 5 Claims.

water impervious, slow-dissolving material. Typical of such materialsare the natural gums, such as gelatine, gum arabic, gum tragacanth, orguar seed gum. Other satisfactory materials are the synthetic materialscommonly used to encapsulate medicines, polyvinyl alcohols, carboxylatedmethyl celluloses, or organic compounds slowly soluble in water such lasbenzoin, camphor or diphenylurea. The granulated, encapsulated explosiveshould have a particle size in the range from about 0.01 -to about 0.25inch and preferably in the range from about 0.05 to about 0.15 inch.

'Ilhe amount of the explosive capsules added to lthe drill- .ing fluidis in the nange from about 0.1 to about l0 lbs. per barrel of drillingliuid. A preferred concentration is from about l to about 5 lbs. perbarrel of drilling fluid. The explosive capsules are preferably added tothe drilling mud intermittently but may be added continuously so long asthe desired -concentration is maintained in the drilling mud and thereis suflicient explosive concentrated in the region of the drill bit orin the lilter cake on the bottom of the well.

`inasmuch as it is necessary for the capsules to dissolve slowly inwater to prevent dangerous accumulation thereof, it is necessary to usean aqueous drilling fluid. In other words, the drilling uid must containwater to contact the encapsulated explosive such that in case any of thecapsules are not exploded by setting down weight thereon by the drillbit, the explosive will be rendered harmless by dissolution of thecapsules `and contact of the explosive with water.

it will be desirable to provide materials as encapsulating agents whichwill dissolve in a period of time such that the encapsulating materialwill slowly dissolve. Thus, the capsules will dissolve at a time withinthe range from l0 minutes to l0 days such that the explosive is renderedharmless. Little, if any, of the explosive will be in the mud returnedto the earths surface in that most, if not all, of that which is notexploded will be dispersed in the filter cake lining the wall of thewell bore. Additionally, the concentration of 0.1 to l0 lbs. of smallgrain encapsulated explosive is such that it will be widely dispersed inthe drilling fluid.

The present invention will be further illustrated by reference to fthedrawing in which:

FIG. l is a flow diagram of a preferred mode; and

FiG. 2 illustrates a mode for encapsulating the explosive.

Referring now to the drawing, numeral 1l designates the earths surfacefrom which a well bore l2 has been drilled by rotating a hollow `drillstring 13 carrying on its lower end a rock bit 14, suitably a toothedbit, but other well-known rock bits may be used. The hollow drill stringextends to the tioor 15 of a derrick 16 wherein it is rotated by arotary table i7 driven by a suitable power means, not shown. Connectedinto the upper end of the Idrill string 13 is a kelly joint 18 whichconnects by means of a swivel 19 to a flexible conduit 20 which, inturn, connects by pipe 2l to a mud pump 22.. Mud pump 22 takes suctionby pipe 2.3 'with the mud pit 24'.

Connected into pipe Z1 by a conduit 27 controlled by a valve 28 is atank 29 which contains a supply of encapsulated explosives. As the mudis drawn into the pump 212 through line 23 and pumped by line 2l asufficient amount of the encapsulated explosive is discharged by line 27into line 2,1 to maintain in the dri-lling mud the desired concentrationof explosive and the mud containing the explosive is then pumped downthe hollow drill string 13 then out through the drill bit liti. Theexplosive then concentrates in the til-ter cake at the bottom of thewell bore and the concentrated encapsulated explosive is then crushed bythe weight of the drill string and thus exploded.

n.9 By virtue of the explosion of the explosive by the drill oit M', the`drilling rate is enhanced to a considerable degree lby microscopicfissures or cracks created under the drill bit by the plurality ofexplosions occurring. This allows the drill bit to fracture the roclf`formation easily and results in increased drilling rates. Not only isthe present invention useful in increased drilling rate but explosionsin the region of drill :bit ld cause microscopic fissures in the rockwhich allows the rock to be fractured easily by the drill bit andrernoved as chips. With generation of gas in the immediate vicinity ofthe roch bit teeth, the pressure dferential :across the rock chips isreduced and the rock chips are efiiciently dislodged and microscopiclissures that are formed are widened rather than healed as encounteredin conventional drilling operations.

The exploding capsules El) thus create a plurality ol miniatureexplosions 3l in the region of the roel; bit ill speedingy the drillingrate and allowing improved drilling operations.

Any of the capsules y.vhich emerge from under the drill bit ltd-withoutexploding are carried into the annulus 32 and deposited in the filtercalce lining the Well bore 'wall and by virtue of the time elapsing, thecapsules are slowly dissolved and the explosives are eventually renderedharinless by Contact with the aqueous drilling llt id.

The present invention is quite advantageous and useful in increasing thespeed or" drilling through earth formations.

Referring novv to FlG. 2, a mode is described of encapsulating thegranulated explosive. ln FlG. 2, numeral 40 designates a hoppercontaining granulated explosive 4l of suliciently small size to formcapsules of a size within the range given. The hopper is controlled byvalve 42 which allows a stream i3 of the granulated explosive 41 to bedischarged into a tank i4 containing a volume 4S of encapsulating agentsuch as has been described. The stream 43 of the granulated explosive l?"alls downwardly within the encapsulating agent i5 and is coated therebyand by gravity ilows into the boot d for removal of the encapsulatingagent 'by way of line 47 controlled by valve 48. The encapsulatedexplosive may then be dried as desired and then placed in the tanl; 29for introduction into line 2l as has been described. While one methodhas been described of encapsulating the granulated explosive, othermethods may be used, For example, the explosive may be encapsulated by aspray-drying technique.

The practice of the present invention has been illus- /l trated byconventional circulation down the drill string7 and up the annulus. ltis to be-understood, however, that reverse circulation may be employedsuch that the mud is flowed down the annulus 32 and up the drill string113. In such instances, of course, it would be necessary to change theflow system to prov-ide for returns of the -mud to the mud pit.

The nature and objects of the present invention having been completelydescribed and illustrated, what we wish to claim as new and useful andsecure by Letters Patent is:

1. An aqueous dri ing fluid comprising drilling mud containing particlesof explosive selected from the group consisting oi lead picrat gulndynamite, mixtures of iercury ulrninate with `potassium perchlorate, andniixtures of antimony trisullde, lead triazide, and nitrogen trilodide iLi dynamite, trinitrotoluene, and pentaerythritol tetrani rate, having adrop sensitivity as measured by the drop sensitivity test within therange *from about 2 to about ll) ein. and having a dry encapsulatingcoating selected from the `group consisting of gelatine, gum arabic, gumtragacanth, guar seed gui-n, polyvinyl alcohol, carboxylated methylcellulose, benzoin, ca'niphor, and diphenyl urea, said particles beingof a size within the range from about 0.91 to about 0.25 inch, thecoating on said particles being water soluble, said explosive beingrendered harmless by contact with water for a time within the range froml0 minutes to 10 days.

2. A drilling fluid in accordance with claim 1 in which the explosive islead picrate.

3. A drilling iluid in accordance with claim 1 in which the explosive isguhr dynamite.

4. A drilling iluid in accordance with claim 1 in which the explosive isa mixture of mercury uilminate and potassium perchlorate.

5. A drilling luid in accordance with claim 1 which contains from about@.1 to about 10 pounds of said particles per barrel of drilling fluid.

References Cited in the le of this patent UNITED STATES PATENTS

1. AN AQUEOUS DRILLING FLUID COMPRISING DRILLING MUD CONTAININGPARTICLES OF EXPLOSIVE SELECTED FROM THE GROUP CONSISTING OF LEADPICRATE, GUHR DYNAMITE, MIXTURES OF MERCURY FULMINATE WITH POTASSIUMPERCHLORATE, AND MIXTURES OF ANTIMONY TRISULFIDE, LEAD TRIAZIDE, ANDNITROGEN TRIIODIDE WITH DYNAMITE, TRINITROTOLUENE, AND PENTAERYTHRITOLTETRANITRATE, HAVING A DROP SENSITIVITY AS MEASURED BY THE DROPSENSITIVITY TEST WITHIN THE RANGE FROM ABOUT 2 TO ABOUT 10 CM. ANDHAVING A DRY ENCAPSULATING COATING SELECTED FROM THE GROUP CONSISTING OFGELATINE, GUM ARABIC, GUM TRAGACANTH, GUAR SEED GUM, POLYVINYL ALCOHOL,CARBOXYLATED METHYL CELLULOSE, BENZOIN, CAMPHOR, AND DIPHENYL UREA, SAIDPARTICLES BEING OF A SIZE WITHIN THE RANGE FROM ABOUT 0.01 TO ABOUT 0.25INCH, THE COATING ON SAID PARTICLES BEING WATER SOLUBLE, SAID EXPLOSIVEBEING REND-